During an engine cold start, an excess of fuel is injected into a motor vehicle engine in order to achieve reliable combustion, increase exhaust temperature and expedite light-off of components such as emission control devices. As a result, there may be an increase in hydrocarbon (HC) in the exhaust and because the emission control devices have not warmed-up (e.g., reached operating temperature), excess HC may be emitted into the atmosphere.
One approach to reduce HC emission during an engine cold start is disclosed in U.S. Pat. No. 5,960,777. In the cited reference, incoming engine intake air is selectively compressed and brought into contact with a membrane structure which separates the air into oxygen and nitrogen enriched fractions. To reduce cold start emissions, the oxygen enriched fraction may be fed to the combustion chamber.
Under some conditions, oxygen enriched air may be needed during an engine start in order to reduce HC emission. With the above approach, because oxygen enriched fractions must be generated as needed, oxygen enriched air may not be sufficiently available right away during engine starting. Further, a compressor is required specifically to generate compressed air during an engine start or, if the compressor is a component of a turbocharger, compressed air may not be generated until the turbocharger starts spinning at a fast enough rate to produce boost.
The inventors herein have recognized the above problems and have devised various approaches to at least partially address them. Thus, a method for generating an oxidant rich component of engine intake air and storing the oxidant rich component is disclosed. The method comprises, under selected operating conditions, generating an oxygen rich component from engine intake air, storing the oxidant rich component of the intake air, and, under subsequent cold start conditions, injecting an amount of the stored oxidant rich component to the engine.
Specifically, in one example, the oxidant rich component of the engine intake air is generated when boost is greater than a threshold amount. In this manner, oxidant rich air is generated during warmed up engine operation, for example, via a turbocharger that is coupled to the engine and the oxidant rich air is stored so that it can be used at a later time, such as during a subsequent engine start. In this way, it is possible to provide an increased amount of oxidant rich air during cold engine starts, if desired, while still using a turbocharger-based compression approach.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.